Remove limits on path lengths and directory entry count

[subtervisor]

Removes the hard-coded limits on path lengths and maximum number of files in a directory.

This allows arbitrarily-long filenames to be loaded, as well as long paths to be saved as the last path. In addition, it removes the 1000 file limit and allows for loading directories of arbitrary size.

[profi200]

Was this tested with very large directories? At some point this will run out of memory and in the future i expect less memory to be available because the planned GUI will eat some of it.

[subtervisor]

I tried with a directory containing 1500 ROMs and it handled it fine. I haven't tried with larger amounts, though it's also worth mentioning that this defaults to smaller amounts. Unfortunately, there's no way to do pagination or anything else, other than maybe re-loading the directory and skipping entries...

[subtervisor]

Is there a way to view available heap space? It would be good to do comparisons and have a way to know whether or not limiting directory size is a premature optimization.

[subtervisor]

Switched over to using FCRAM for the built up directory entries structure to avoid having to worry about memory limits (128MB seems like more than enough to handle the directory browsing/GUI memory needs, imo)

It also adjusts the code to handle arbitrary-length basepaths properly